Audio File Size Calculator
Pick the sample rate, bit depth and channels (or an MP3, AAC or Opus bitrate) and the length: get the exact bytes, the MB and what Windows will show you. Or the other way round: how much audio fits on your card.
Your recording
How audio file size is calculated
Uncompressed audio (WAV, AIFF, BWF) stores every sample of every channel as is, so its size is plain multiplication:
At CD quality that is 44,100 × 16 × 2 = 1,411,200 bits per second (1411.2 kbps), or 176,400 bytes per
second: 10,584,000 bytes per minute. 24-bit samples take 3 bytes and 32-bit float ones take 4. A PCM WAV
adds a 44-byte header; a BWF adds its bext chunk (602 bytes plus the coding history). The
calculator shows the audio bytes only: the header is negligible (44 bytes against the 10,584,000 of a CD minute).
Bitrate-based audio (MP3, AAC, Opus, Vorbis) is sized by its bitrate, which already covers every channel:
One kbps is 1000 bits per second, not 1024: that is how encoders count (Opus takes its bitrate in bits per
second; in FFmpeg, 128k means 128,000). At a constant bitrate (CBR) the result is exact for the audio; with
VBR it is an average. Results are in decimal MB (1 MB = 1,000,000 bytes), like the rest of the site, with
MiB (1,048,576 bytes) alongside, which is what Windows calls "MB".
Example: file size of 1 hour of 48 kHz 24-bit WAV audio
Say you record production sound as 48 kHz, 24-bit, stereo WAV for 1 hour:
- 48,000 samples × 3 bytes × 2 channels = 288,000 bytes per second (2304 kbps).
- 288,000 × 3,600 s = 1,036,800,000 bytes = 1.04 GB (17.28 MB per minute).
- Windows will show it as 988.8 MiB, labelled "MB": the same bytes in another unit.
- It fits in a WAV with room to spare: in this format the cap is 4 h 8 min 33 s.
The same hour as 320 kbps MP3 takes 144 MB, and at 128 kbps, 57.6 MB. A 2-hour 5.1 mix at 48 kHz 24-bit is already 6.22 GB: it does not fit in a WAV and needs RF64/BW64 (or splitting).
The 4 GB WAV limit: how much audio fits in one file
RIFF/WAVE stores every size in an unsigned 32-bit field, so a WAV or BWF file cannot exceed 4 GiB (4,294,967,296 bytes). Minus the smallest header, that leaves 4,294,967,258 bytes of audio. Some programs read that field as a signed integer and already fail past 2 GiB. This is the longest single file, rounded down to the second:
| Format | Maximum (4 GiB) | Compatible (2 GiB) |
|---|---|---|
| 44.1 kHz · 16-bit · stereo | 6 h 45 min 47 s | 3 h 22 min 53 s |
| 48 kHz · 16-bit · stereo | 6 h 12 min 49 s | 3 h 6 min 24 s |
| 48 kHz · 24-bit · mono | 8 h 17 min 6 s | 4 h 8 min 33 s |
| 48 kHz · 24-bit · stereo | 4 h 8 min 33 s | 2 h 4 min 16 s |
| 48 kHz · 32-bit float · stereo | 3 h 6 min 24 s | 1 h 33 min 12 s |
| 48 kHz · 24-bit · 5.1 | 1 h 22 min 51 s | 41 min 25 s |
| 96 kHz · 24-bit · stereo | 2 h 4 min 16 s | 1 h 2 min 8 s |
| 192 kHz · 24-bit · stereo | 1 h 2 min 8 s | 31 min 4 s |
Beyond that there are RF64 (EBU Tech 3306) and BW64 (ITU-R BS.2088), which add a
ds64 chunk with 64-bit sizes. Headers larger than the minimum (extensible WAV, float, BWF with metadata) trim
these caps by a fraction of a second.
Methodology & sources
Every result is computed in your browser with the formula shown above — nothing is sent to a server. The numeric model is based on this data and these references:
- IBM & Microsoft — Multimedia Programming Interface and Data Specifications 1.0 (1991): the RIFF/WAVE format, 32-bit chunk sizes and the pad byte
- Microsoft — WAVEFORMATEX: nBlockAlign = channels × bits ÷ 8 and bytes per second
- EBU Tech 3285 v2 — Broadcast Wave Format (BWF)
- EBU Tech 3306 — RF64: the 4 GB limit of RIFF/WAVE and its 64-bit extension
- ITU-R BS.2088 — BW64, long-form file format for audio exchange
- Opus — the API sets the bitrate in bits per second (1 kbps = 1000 bit/s)
- FFmpeg — the k, M and G prefixes are powers of 1000 (with "i", of 1024)
- Apple — how storage capacity is measured (decimal GB)
- Results in decimal units (1 MB = 10⁶ bytes, 1 GB = 10⁹ bytes) and, separately, in MiB/GiB (2²⁰/2³⁰ bytes), which is what Windows labels "MB"/"GB". Cards in GB as sold, with a 2% safety margin.
Formula reviewed and verified against real-world cases.